How to Replace a Toilet Flapper (Step-by-Step)

Scope of this guide: This page covers one specific running-toilet repair: replacing the flapper. Use the broader troubleshooting and cost guides when the flapper is not the cause.

A running toilet is one of the most common and wasteful home plumbing problems. The culprit is almost always the flapper - the rubber seal at the bottom of the toilet tank that controls water flow into the bowl. Replacing it is one of the easiest plumbing repairs a homeowner can do, and the part typically costs just a few dollars.

What the Flapper Does

When you flush, the handle lifts the flapper via a chain, allowing water from the tank to rush into the bowl. Once the tank empties, the flapper drops back down and seals the drain hole so the tank can refill. If the flapper does not seal properly - because it is warped, cracked, or coated in mineral buildup - water continuously trickles from the tank into the bowl, causing the fill valve to run constantly.

To confirm the flapper is the issue: drop a few drops of food coloring into the tank and wait ten minutes without flushing. If color appears in the bowl, the flapper is not sealing.

What You Need

• A replacement flapper (bring the old one to the hardware store to match the size and style - universal flappers fit most toilets, but some brands require a specific type)
• Your hands (no tools needed for most installations)

Step-by-Step Replacement

Step 1: Shut off the water. Find the shutoff valve behind or below the toilet, on the supply line coming out of the wall or floor. Turn it clockwise until it stops.

Step 2: Flush the toilet. This empties the tank and gives you a dry workspace.

Step 3: Remove the tank lid. Set it aside carefully - porcelain lids chip and crack easily.

Step 4: Disconnect the chain. The flapper is connected to the flush handle arm by a chain. Unhook the chain from the handle arm (not the flapper end yet).

Step 5: Remove the old flapper. Most flappers have two ears that loop over pegs on either side of the flush valve - the central column at the bottom of the tank. Slide the ears off the pegs to release the flapper. If the flapper has a ring that fits around the overflow tube instead of ears, pull it straight up.

Step 6: Note the style. Before discarding the old flapper, look at how it was attached - ears on pegs, ring over tube, or another style. Your replacement needs to match.

Step 7: Install the new flapper. Snap or slide the ears onto the pegs (or slip the ring over the overflow tube). Make sure it sits flat and centered over the drain opening.

Step 8: Reconnect the chain. Attach the chain to the flush handle arm. Leave about half an inch of slack. Too much slack and the flapper will not lift fully on flush. Too tight and the flapper will not seat properly and will keep running.

Step 9: Turn the water back on. Open the shutoff valve slowly. Let the tank fill, then flush and watch the flapper seat itself. Check that the running has stopped.

Common Problems After Replacement

Still running: The chain may be too tight, catching under the flapper and preventing a full seal. Adjust the clip position on the chain to add a bit more slack.

Weak flush: The chain has too much slack and the flapper is not lifting high enough. Move the clip a few links shorter.

Flapper not seating flat: Check that the flapper is centered and that no part of the chain is caught underneath it.

When to Call a Plumber

Sources and editorial notes

Prices and permit requirements vary by location, property, equipment, and scope. Treat price ranges as planning estimates and confirm current requirements with the relevant authority and contractor.

• US Small Business Administration - business guide

Related guides

• How to Unclog a Toilet Without Calling a Plumber
• How Much Does It Cost to Fix a Running Toilet?
• How to Stop a Toilet from Running (Step-by-Step)

Next step

Need professional help? Describe the job with Aniva and connect with local service providers.